Create a hanging garden at home
Hanging gardens and other green roofs are growing in France, with 200,000 square meters installed each year. A market still in its infancy compared to countries like Japan, Holland or Germany (13 million square meters). In the context of sustainable development, these plant spaces are ecological and trendy. They are also particularly aesthetic, provided they are well thought out and maintained. It is better to be properly informed before embarking on the adventure, because the thickness of the soil varies greatly depending on the desired result.
From aesthetics to ecological utility
A beautiful green terrace attracts and soothes the eye, especially in urban areas. This aesthetic character has been symbolized since Antiquity by the famous and stupendous Hanging Gardens of Babylon, built on terraces 120 meters long, and listed as one of the Seven Wonders of the Ancient World - although their actual existence still remains uncertain. Nowadays, multiple examples of great contemporary achievements exist all over the world.
Japan is one of the countries most involved in this field, notably with the vast Namba Parks inaugurated in 2003 in Osaka: 11,500m² of greenery and 70,000 plants and trees in a shopping center.
To rediscover a little of the magic of the Hanging Gardens of Babylon, you will have to go to Dubai and contemplate the stunning Park Gate. Six enormous 40-story towers were completed in 2011; it is planned to link them all together by a gigantic “green cave”, where vegetation will be fixed.
In a less aerial and more accessible way, hanging gardens can also be made by individuals on their terrace, or directly on the roofs (and even on a slope). In addition to their aesthetic appearance, these installations have several advantageous qualities. The investment costs are effectively amortized over time, thanks to the quality of life provided by green roofs.
They are indeed excellent thermal and acoustic insulators, which appreciably attenuate temperature variations, correspondingly reducing energy expenditure, and also help to limit the accumulation of heat in cities. Moreover, in urban areas, these installations actively participate in filtering toxic gases and microparticles released by vehicles. Finally, in the case of sufficiently deep green roofs, these constitute potential places for organic cultivation, larger than the few square meters of a simple balcony.
Design a green roof or a hanging garden at home
Ecological enthusiasm and goodwill are not enough to create serious and lasting green roofs. Several parameters govern their proper use.
The thickness of the substrate used varies according to the objectives sought, and above all according to the strength of the roof. From 3 to 7 cm, we speak of extensive revegetation, using hardy plants requiring little maintenance. Up to 15 cm, it is semi-extensive revegetation, with perennials requiring more maintenance. Beyond these depths, it is possible to speak of real hanging gardens (intensive revegetation) admitting the planting of vegetables and even small trees, but requiring a solid concrete support and great attention.
If hanging gardens logically require horizontal ground, the shallow depth of the extensive and semi-extensive vegetation allows the design of spectacular sloping roofs. In all cases, these types of achievements require ensuring the solidity and perfect waterproofing of the roofs considered, at the risk of putting off insurance companies. For semi-extensive roofs and hanging gardens, maintenance must be supported at the risk of seeing a natural wasteland develop at best, as in a “terrestrial” garden, or at worst damage to buildings. Finally, in urban areas, these facilities are particularly exposed to the risks of storms and heat waves, requiring a sound initial design.